Introduction to Lighting

Colour Tempreautre
 
White light isn’t always the same white. This is more evident in buildings that have a combination of incandescent tungsten and fluorescent lights.
 
Colour Temperature is measured in Kelvins (K) and is related to the physical phenomenon of black body radiation. When a body of matter that is opaque and non-reflective is held at a constant uniform temperature it glows, emitting electromagnetic radiation at a specific spectrum and intensity depending on the temperature. Kelvins are the standard international unit of temperature. Bodies at 1,000K glow a reddish hue and hotter objects progress through orange, yellow and eventually blue hues.
 
Daylight can vary from 5,000-6,500K, depending on the time of day and cloud cover. Lights and cameras are made to have daylight set to an arbitrary figure, usually around 5,600K.
 
Many studio lights use tungsten bulbs which have a colour temperature of about 3,200K.
 
Compared to daylight, tungsten lights appear redder
 
Fluorescent lights traditionally have a colour temperature of about 5,000K. With the shift towards compact fluorescent bulbs for domestic use, many manufacturers have made compact fluorescent bulbs that are balanced to around 3,200K, to mimic the tungsten light that is more familiar to people at home.
 
Compared to tungsten lights, fluorescent lights and daylight appear bluer
 
There are filters (“gels”) that can be placed over lights that change the colour temperature of a light from tungsten to daylight (CTB) and from daylight to tungsten (CTO)